Prediction of Binary VLE for Imidazolium Based Ionic Liquid Systems Using COSMO-RS

Abstract

A novel method based on unimolecular quantum mechanical calculation has been used to predict the binary vapor−liquid equilibria (VLE) of ionic liquids (ILs).The recently developed conductor-like screening model (COSMO), along with the most common quantum chemical package of GAUSSIAN 03, has been used in this work. These conductor-like screening model calculations combined with exact statistical thermodynamics provide the information necessary for the evaluation of molecular interactions in liquids. An effective parametrization has been done using 10 associated and 22 binary nonassociated systems; these 32 systems are all non-ILs. The effective contact surface area a eff and the hydrogen-bonding coefficient c hb have been estimated using a sequential scheme. The root-mean-square error obtained for excess Gibb's free energy is ∼0.1 for a eff and c hb. Values for α‘ (misfit constant), σhb (cutoff surface charge density for hydrogen bonding), and cavity radii (r i ) as given in the literature have been used as default. COSMO-RS has then been used to predict the vapor−liquid equilibria for 116 non-IL binary sets out of which 33 are azeotropic systems. COSMO-RS predicts a better pressure a priori with a relative error of ∼4%, as compared to a 7−8% error for the Wilson/NRTL/UNIQUAC models. Being an a priori model, it does fall short with respect to absolute average deviation in mole fraction for the vapor phase: 0.025 as compared to ∼0.0075 for the Wilson, NRTL, and UNIQUAC models. Having thus benchmarked extensively, the COSMO-RS model has then been used to predict the VLE for 13 systems based on five imidazolium ILs: (a) 1-methyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [MMIM] [(CF3SO2)2N] with (1) benzene and (2) cyclohexane; (b) 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [EMIM][(CF3SO2)2N] with (3) acetone, (4) 2-propanol, and (5) water; (c) 1-butyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl) imide [BMIM][(CF3SO2)2N] with (6) acetone, (7) 2-propanol, and (8) water; (d)1-methyl-3-methylimidazolium dimethylphosphate [MMIM][(CH3)2PO4] with (9) acetone, (10) tetrahydrofuran, and (11) water; and (e) 1-ethyl-3-methylimidazolium ethoxysulfate [EMIM][C2H5OSO3] with (12) benzene and (13) cyclohexane. The root-mean-square deviation for pressure prediction is 6% as compared to 4%, 1.45%, and 3.13% for the Wilson, NRTL, and UNIQUAC models, respectively. The mole fraction in the vapor phase has also been predicted, confirming the negligible presence of ionic liquids in the vapor phase even at very low pressures.

Quantum chemical studies on the simultaneous interaction of thiophene and pyridine with ionic liquid

“…LLE of ionic liquid (1-alkyl-3-methylimidazolium methylsulphate) with alcohols, ethers, and ketones have been predicted using COSMO-RS model by Domanska et al 38 They also predicted the binary LLE for the IL system namely 1,3-dimethylimidazolium or 1-butyl-3-methylimidazolium methylsulfate with hydrocarbons such as benzene, toluene, ethyl benzene, propylbenzene, o-xylene, m-xylene, and p-xylene at atmospheric pressure. 39 In our earlier work, COSMO-RS model have successfully used for the prediction of binary VLE 40 and ternary LLE 41,42 of imidazolium based ionic liquid. Additionally, infinite dilution activity coefficients (IDAC) values of solutes in ILs were successfully predicted by Klamt et al 43 and Banerjee et al 44 The expression and methodology are given in details in our previously published work on COSMO-RS model.…”

“…Additionally, infinite dilution activity coefficients (IDAC) values of solutes in ILs were successfully predicted by Klamt et al 43 and Banerjee et al 44 The expression and methodology are given in details in our previously published work on COSMO-RS model. [40][41][42]44 The quantum chemistry package of Gaussian 03 24 has been used to compute the COSMO files. The first step for COSMO-RS calculation is to estimate the sigma profile of each species.…”

Application of a Thermodynamic Consistency Test to Binary Mixtures Containing an Ionic Liquid

“…(18) and (19). As a comparison, Banerjee et al [25] predicted y fluid values in the range 0.99-1.00.…”

Extraction of Phthalic Acid from Aqueous Solution by Using Ionic Liquids: A Quantum Chemical Approach

“…The interaction energies within the segments and the methodological analysis for obtaining the equations are reported in our earlier work [30,31]. We have reimplemented the COSMO-SAC model as given by Sandler and Lin [28].…”

“…The interaction energies are described by the COSMO-RS parameters. Parameter values used in the COSMO-RS model is surface area of a standard segment (a eff ) = 6.25 Å 2 , misfit constant for misfit energy interaction (α′)= 8896 (kcal Å 4 )/ (mol e 2 ), constant for hydrogenbonding interaction (c hb )=54874(kcal Å 4 )/(mol e 2 ), and the cut off value for hydrogen-bonding interactions (σ hb )=0.0085e/ Å 2 and are taken from previous work [30,31].…”